1. Technical Field
The present invention relates to a medium feeder for transporting a medium and an image reading apparatus having the medium feeder.
2. Related Art
Some types of scanners, as examples of image reading apparatuses, include an automatic document feeder (ADF) serving as a medium feeder for allowing multiple document sheets to be fed and scanned automatically. Such a medium feeder may have an edge guide that is provided at a medium tray on which a stack of document sheets to be fed is placed. The edge guide guides the side edge of the document sheet in a width direction parallel to the width of the document sheet. For example, a medium feeder disclosed in Japanese Patent No. 5,810,769 has an edge guide that is slidable in the width direction in accordance with the size of the document sheet.
A medium feeder often has an upper limit on the number of document sheets mountable on a medium tray to ensure proper feeding of the document sheet. When a medium tray or a feed tray is open at the top, such as disclosed in Japanese Patent No. 5,810,769, a user may set document sheets above the upper limit on the medium tray. Mounting document sheets above the upper limit on the medium tray may cause a so-called misfeed in which no document sheet is fed.
To prevent such an error, JP-A-2001-106362 discloses an upper limiter that is provided at an edge guide to limit the number of sheets being stacked on a medium tray.
In JP-A-2001-106362, media are inserted between the upper limiter and the mounting surface of the medium tray, and the number of media being stacked on the medium tray is limited when the upper limiter comes into contact with the top medium in the stack. However, there is likelihood that media may be inserted through a gap between the upper limiter and an apparatus housing from above the upper limiter without passing between the upper limiter and the mounting surface of the medium tray. In this case, the media may enter a nip section of feed rollers at an improper angle that causes a misfeed.
A contact surface of the upper limiter faces the mounting surface of the medium tray and comes into contact with the top medium in the stack. The gap between the upper limiter and the apparatus housing can be reduced or removed by elongating the contact surface in a downstream direction in which the medium is fed. However, the elongation of the contact surface increases friction with the medium caused when the medium is fed. The increased friction may also cause a misfeed.